1. Field of the Invention
The present invention relates to a method for effectively reducing noise, and more particularly, to a method for effectively reducing noise while processing video signals.
2. Description of the Related Art
The video signal media is currently considered the most powerful media for transmitting message, and the digital signal processing is widely applied in the video signal applications. An HDTV (High Definition Television) is a technique heavily relied on utilizing the digital processing. Since various noises are contained in the analog step of video signal digitalization, in order to eliminate the undesired noise, an image processing technique has to be applied to filter out the undesired noise in the signal that makes human eyes uncomfortable.
The video signal usually means the motion picture image, thus the image processing technique is an essential part of the video signal processing techniques. Since the image is two-dimensional (2D), the method for processing a 2D signal is slightly different from that used for processing a typical one-dimensional (ID) signal. The most essential method for processing 2D image is using 2D FFT (Fast Fourier Transformation) and 2D convolution operations. By using 2D FFT, the 2D image is converted into a 2D spectrum. The signal having a specific frequency is then attenuated to a certain level, and the 2D spectrum is recovered to the original image by a 2D reverse FFT, such that the specific noise in the picture is eliminated.
FIG. 1 schematically shows a conventional apparatus for noise reduction, which comprises an adaptive spatial filter set 10 and an adaptive temporal filter set 30. After an unprocessed video signal p (i, j, t) is input into the adaptive spatial filter set 10 and has been undergone an adaptive spatial filtering, a basic signal z (i, j, t) is generated. Then, after the basic signal z (i, j, t) has been undergone an adaptive temporal filtering by the adaptive temporal filter set 30, a processed video signal y (i, j, t) is obtained. Since the noise reduction in such configuration is limited by using the specific parameter of a single filtering band, the result of the noise reduction is poor. Therefore, the present invention is aimed on a more effective way to resolve this issue.